The present invention relates to an efficient method and system for online monitoring of a short circuiting gas metal arc welding process to determine weld quality, process stability, and geometry estimation.
Gas metal arc welding (hereinafter xe2x80x9cGMAWxe2x80x9d) of automotive thin sheets involves the use of low currents, preferably less than 150 amps, for causing transfer of metal to occur when the welding apparatus is in a short-circuiting mode. GMAW is commonly operated in automatic or semiautomatic modes and utilized in high production welding operations. However, the practice of short-circuiting GMAW to consistently produce high quality welds is regarded generally as quite difficult due to a resulting intermittent welding arc and short-circuiting metal transfer.
Existing methods for inspecting the quality of welds include, for example, trial and error, visual inspection, destructive testing, and arc sensing. Current industry methods of monitoring welding processes and weld quality are thus heavily dependent on the knowledge, sensory perception and experience of welders, which render the methods labor-intensive, subjective and frequently inefficient. They also tend to involve analysis that occurs after the weld has been made; and do not allow for an early opportunity to scrap a part or take remedial measures to fix the weld.
It would be desirable to be able to continuously monitor weld stability, quality or geometry during a welding process, in real-time. It would be especially desirable to have a system that, based upon feedback from the monitoring, could adjust one or more welding process parameters for improving weld stability, quality or geometry (e.g., the weld length, the sample rate frequency, the short-circuiting current, the arc current, the short-circuiting voltage, the arc voltage, or otherwise).
The present invention provides an efficient method and system for meeting the above desires, by providing an improved approach for analyzing the stability of metal transfer and the weld quality in a short-circuiting gas metal arc welding process. The method and system use the welding current and voltage signals produced during the welding process and therefore, require no additional sophisticated hardware be added to the whole welding system. The system is particularly useful, when used in accordance with the present invention, for analyzing the process stability and weld quality of GMAW of low carbon sheet steel.
The system can monitor every welding process and record the quality information into a quality management database for statistical analysis and process control. More particularly, a graphical user interface (hereinafter xe2x80x9cGUIxe2x80x9d) can display welding signals, signal processing results, stability analysis results, weld-quality information to detect signal welding problems, monitor weld quality, improve weld quality, and thereby, increase productivity.
More particularly, the online monitoring system for monitoring a welding process comprises:
(a) a computer having
(i) a controlling microprocessor, and
(ii) a graphical user interface;
(b) at least one welding machine in operable communication with the computer;
(c) a communication interface for interfacing communication between the at least one welding machine and the computer;
(d) a data acquisition system in operable communication with the controlling microprocessor and in further communication with the at least one welding machine for acquiring welding signal data from the at least one welding machine, the data acquisition system having an associated memory means;
(e) a quality management database for storing at least one of welding signal data, monitoring results, and diagnostic results in the data acquisition system associated memory means; and
(f) a statistical signal processing system in communication with the data acquisition system for processing the welding signal data stored in the data acquisition system associated memory means and in further communication with the communication interface for communicating processed welding signal data to the GUI.
Additionally, there is provided a method of use of the online monitoring system to monitor and control a gas metal arc welding process according to a user defined format comprising the steps of:
a) setting welding and data acquisition parameters;
b) setting a welding voltage""s first rising edge as a triggering signal to start a data acquisition process;
c) determining whether the triggering signal was received;
d) waiting for a triggering signal if a triggering signal was not received;
e) determining whether to perform an off-line signal analysis if a triggering signal was not received;
f) repeating steps c)-e) if an off-line signal analysis is not needed;
g) performing an off-line signal analysis if an off-line signal analysis is needed;
h) loading existing voltage and current data stored in a data acquisition memory means when an off-line signal analysis is performed;
i) acquiring current and voltage from an active welding cycle upon receiving a triggering signal;
j) performing signal processing algorithms on the acquired or the loaded current and voltage data.